As a general matter:
1. Save often. If you lose two or three characters in a fight, reload and try a different approach. Later, when you're on firmer footing with combat and res scrolls, you can go back to riding out suboptimal results.
2. If a battle seems impossible, leave it for now and come back when you've gained some levels and found/bought better gear.
3. Use the environment to your advantage. Several early fights give you a chance to use height to your advantage. Try splitting your party and sneaking to get everyone in favorable position. If you know a fight will start after a conversation, split off the non-speaking party members to get them in position. The last thing you want is for ambush your entire party with one spell.
4. Focus on stealing enemies' turns and adding more for yourself. You'll notice that many skills have a negative status effect that will apply once the enemy is stripped of the relevant armor type. Very early in the game, you will have access to tentacle lash, chicken claw, and battering ram. The first prevents an enemy from using its weapon for a turn, the other two prevent enemies from doing much of anything for a turn. Getting an enemy off your back for even one turn is super valuable! To that end, you should try to get "teleport" on at least two party members. Early on, enemies don't have as many mobility spells, so simply teleporting them far away will buy you some time. You can also use this to deal with obnoxious snipers by bringing them down from their purchases and right to your party.
You can also add to your turns by making someone in your party a summoner. One more character applying damage (and soaking it up, if the enemies focus on the summoned creature) is very powerful in the early game.